1. Field
One embodiment of the invention relates to a printed circuit board for mounting a semiconductor component thereon, and an electronic device.
2. Description of the Related Art
Recently, memory chips for use as semiconductor components have been highly developed in terms of density and capacity and have been provided in the form of, for example, a ball grid array (BGA) package. Further development of the structures of the packaged memories continues to strive to fulfill the requirement for making a silicon chip that has, on the one hand, a larger memory chip, and a more compact package on the other hand. Therefore, the BGA package incorporating such a memory chip suffers more from heat stress in that expansion of the silicon chip due to temperature increases when operating and contraction when not operating are repeated. Such a silicon chip is connected to a substrate by bonding wire or the like and is connected to an external joining electrode that has solder balls provided on the underside of the substrate.
The printed circuit board on which a semiconductor package like the foregoing BGA is mounted requires a highly reliable, stable pattern formation (i.e., circuit formation) to be maintained despite elastic deformation (i.e., expansion and contraction) of the wiring board face when subjected to such heat stress as described above.
A technology for forming a pattern on a printed circuit board for mounting such a semiconductor package has been proposed in Jpn. Pat. Appln. KOKAI Publication No. 2000-261110, in which at least the main parts of leader lines formed on the substrate surface (i.e., surface layer), which main parts are close to the corresponding electrode pads, radiate inward from the corresponding electrode pads and around the deformation center on the substrate. However, in this pattern formation technology, the wiring patterns radiate from the center of a package mounting face. Accordingly, excessive stress may be applied to each of the led wiring portions (e.g., a copper foil portion on the boundary between the pad and the leader line) due to elastic deformation of the wiring board when subjected to heat stress as described above, and is highly liable to cause contact failure, disconnection, etc., of the wiring portion.